The question that you're circling, but can't seem to put your finger on is "if they weren't concerned with oil's future, why would they diversify?"
Historically, oil has gone gangbusters. I doubt any of the sovereign wealth funds lost money buying oil stocks. Yet, within a decade, we've seen a few of them announce that they're going to diversify. Ostensibly, this is a move to stabilize their long-term value against market fluctuations, but given the criticality of energy and how well historically these companies have done, it seems more likely that they're worried about a major market shift on the 30-50 year horizon and are looking to reposition themselves ahead of when the market itself moves.
So to me, it looks like major oil producers are preparing to leave oil, when viewed through a generational lens -- the wealth funds are clearing out, educational training programs are shifting, etc.
In 10-15 years, the flow of new workers will hit whatever low-level long-term carrying will be; in 30-40 years, oil will have settled into some kind of "post primary energy" role. (It's not like petrol products are suddenly not useful; just the bulk of traffic will shift, and so there won't be enough business to support several nations.)
Of course, 2050-2060 was when people were guessing that was going to happen for quite a while. But this seems like a sign we're on track for that, broadly speaking.